The “wedge-shaped sheet waveguide,” also known as the “wedge flat panel display,” is a novel projection display technology. A representative wedge flat panel display is disclosed in WO 01/72037 “Waveguide Display” by Dr. Adrian Robert Leigh Travis. The wedge flat panel is essentially a wedge shaped panel, allowing the image projected by a projector magnified within the panel. In such a display system, the image source enters the display panel from the bottom or from the edge of the screen rather than from the rear of the display screen, whereby greatly reduces the depth of the device.
The most recent type of the wedge flat panel display consists of a planar waveguide and a wedge waveguide, with a carefully designed architecture that enables the projected image pixels to align in a correct order when displayed and the optical path to fold within the waveguide, to magnify the image within the thin space of the planar and the wedge waveguides.
The wedge shaped panel also benefits from the low material cost as the panel can be made from conventional acrylic materials, such as PMMA. The wedge shaped panel is a bi-directional light path, which means that the panel can be used as the lens for a camera to collect the incoming lights/images.
The wedge flat panel display provides the benefits of low-cost and space saving ability. Its drawback, however, is the image band gaps, i.e. the “dark zones” that are easily found in the displayed images. The dark zones, which separate the image into bands, are unacceptable if the wedge waveguide to be used for display purposes. A technique that eliminates the image band gap is to place a diffusive screen at a correct distance gap away from the waveguide. However, this image band gap elimination technique causes distortions when it is used for a thick wedge waveguide device or a device with pixels much smaller than the thickness of the wedge waveguide.
A technology to remove the image band gap is called the “gapless profile wedge.” This technology is disclosed in the U.S. Pat. No. 7,410,286, “Flat-panel display using tapered waveguide,” to Dr. Travis. The basic idea of the gapless profile waveguide panel is to calculate a wedge waveguide surface profile with the final output image not separated by the dark zones. This is done by dividing the surface of the wedge waveguide in to sections orthogonal to the image ray paths and calculating the critical thickness and the length of each section, allowing the image rays to exit the panel via the critical angle after the same number of double bounces within the panel. In the gapless profile wedge waveguide/display, a wedge display and a flat slab waveguide are provided.
The main problem of the gapless profile algorithm is the overlapping of the image occurred in the display panel, as known as the overlapping distortion. This is created by the sharp angle transition in the upper surface from the flat slab waveguide region to the tilt wedge waveguide region (known as the “kink”) that makes those image rays intercepting at the upper surface in the areas just before and after the kink and overlapping each other. As a consequence, the final output image is damaged by the overlapping distortion.
Another problem with the gapless profile algorithm is that the surface profile calculated by the gapless profile algorithm assumes all the image rays exit the panel after the same number of bounces, when the thickness of the waveguide is infinitesimally thin. In the case of a display panel with a finite thickness, the gapless profile algorithm would cause distortions to the images as the rays exit the panel after different number of bounces.
The insertion of a curved waveguide called the “transition waveguide” between the slab waveguide and the wedge waveguide was proposed by A. Travis et al. as a possible solution to the image overlapping distortion, as described above, in their US published patent application No. 2004/0095560. The curved waveguide replaces the sudden angle change (or the kink) at the upper waveguide surface by a surface with a smooth curve, such that the image rays do not overlap each other.
To design the transition waveguide for a wedge display panel, it is difficult to find a rule in the determination of the optimal length and the shape of the transition waveguide curve. The shape and the length of the transition waveguide have significant influence on the image rays' propagation within the wedge panel. However, it is still not possible to identify the optimal shape and length of the transition waveguide curve, giving all the known parameters regarding the image rays, the slab waveguide and the edge waveguide. It is also found that inserting a smooth transition waveguide without modifying the wedge waveguide surface profile would cause the rays to undergo a different number of bounces before they exit the panel.
It is therefore necessary to provide a novel structure of the flat panel display device that uses a waveguide/display panel with substantially the wedged shape.
It is also necessary to provide a flat panel display device that can eliminate the image band gap in the displayed image.
It is also necessary to provide a flat panel display device that is low cost and easy to fabricate.
It is also necessary to provide a flat panel display device that may enhance the quality of the image displayed.
It is also necessary to provide a flat panel display device with a friendly interface to other image processing or optical components.
It is also necessary to provide a flat panel display device wherein the geometric shape of the display panel is not limited to any particular shape.
It is also necessary to provide a flat panel display device with the geometric shape not limited to any particular shape.
It is also necessary to provide a new approach in designing the shape and optical profile of the flat panel display device.
It is also necessary to provide a new method to simplify the design in the shape and optical profile of the flat panel display device.
It is also necessary to provide a method for the design in the structure and optical profile of a flat panel display device with enhanced quality in the image displayed.
It is also necessary to provide a method for the design in the structure and optical profile of a flat panel display device with a friendly interface to other image processing or optical components.
It is also necessary to provide a method for the design in the structure and optical profile of a flat panel display device wherein the geometric shape of the display panel is not limited to any particular shape.
It is also necessary to provide a method for the design in the structure and optical profile of a flat panel display device with the geometric shape not limited to any particular shape.